An inkjet printing system, as one embodiment of a fluid ejection system, may include a printhead, an ink supply that supplies liquid ink to the printhead, and an electronic controller that controls the printhead. The printhead, as one embodiment of a fluid ejection device, ejects ink drops through a plurality of orifices or nozzles. The ink is projected toward a print medium, such as a sheet of paper, to print an image onto the print medium. The nozzles are typically arranged in one or more arrays, such that properly sequenced ejection of ink from the nozzles causes characters or other images to be printed on the print medium as the printhead and the print medium are moved relative to each other.
In a typical thermal inkjet printing system, the printhead ejects ink drops through nozzles by rapidly heating small volumes of ink located in vaporization chambers. The ink is heated with small electric heaters, such as thin film resistors referred to herein as firing resistors. Heating the ink causes the ink to vaporize and be ejected through the nozzles.
To eject one drop of ink, the electronic controller that controls the printhead activates an electrical current from a power supply external to the printhead. The electrical current is passed through a selected firing resistor to heat the ink in a corresponding selected vaporization chamber and eject the ink through a corresponding nozzle. Known drop generators include a firing resistor, a corresponding vaporization chamber, and a corresponding nozzle.
A fluid ejection system is one embodiment of a microelectromechanical system (MEMS) device or semiconductor device. Typically, the size of a MEMS device is determined by the mechanical requirements of the device. Any cost associated with integrating and accommodating electronic circuitry in a MEMS device is transferred to the final cost of the device. It is important to have a low cost process that can integrate increased functionality into a MEMS device. In a process for integrating electronic circuitry into a MEMS device, layout techniques are needed that reduce device sizes and achieve increased functionality.
For these and other reasons, there is a need for the present invention.